Use of carbon dioxide generated in manufacturing synthetic hydrocarbon chains

ABSTRACT

The invention relates to the use of a carbon dioxide stream generated in oxygen gasification of organic matter for carbonating calcium from a liquid containing calcium ions. The invention also relates to a manufacturing process of paper or board, wherein organic matter is gasified with oxygen in order to carbonate the calcium, the produced carbon dioxide stream is reacted with a liquid containing calcium ions and the carbonated calcium is added to the pulp during the papermaking process as a filler or onto finished paper as a coating.

TECHNICAL FIELD

The invention relates to the use of a carbon dioxide stream generated inoxygen gasification. More specifically, the invention relates to the useof the carbon dioxide stream generated in the oxygen gasification oforganic matter for carbonating calcium from calcium-rich liquid, as wellas to a papermaking process, in which the calcium carbonate precipitatedby using the carbon dioxide stream generated in oxygen gasification isadded to paper.

BACKGROUND OF THE TECHNIQUE

The limited supply of fossil fuels, as well as the emissions resultingfrom their use, have lead into added pressure for developing productionmethods of more environmentally-friendly fuels. The use of biomass as anenergy source and especially in the production of fuels is one attempttowards diminishing environmental load in the future.

In regard to energy production, biomass mainly refers to various typesof organic waste, i.e. waste that is of biological origin, for instancewood, agricultural waste, municipal waste, waste land or plants. Theprocess of burning biomass releases energy, referred to as bioenergy,but biomass may also be treated by other methods in order to achieveimproved efficiency and smaller emissions.

Lately, attempts have also been made to use biomass in the production ofliquid fuels, in which case the biomass is first gasified, and theobtained gas is transformed into biofuel. This multi-step process isreferred to as Biomass to Liquid (BLT).

Gasification is an exothermic process, wherein a carbon-containingmaterial, such as biomass, is converted into carbon monoxide andhydrogen. Three reactions occur in the gasifier, namely pyrolysis, inwhich volatiles are released and charcoal is produced, the combustionprocess, in which the volatile substances and some of the charcoal reactwith oxygen to form carbon dioxide and carbon monoxide, and the actualgasification reaction, in which charcoal reacts with carbon dioxide andsteam forming carbon monoxide and hydrogen. Both pyrolysis andcombustion are extremely rapid reactions. In the presence of steam andoxygen, a synthesis gas mixture is formed in the gasifier in accordancewith the following reactions:

C+H₂O →CO+H₂  (1)

C+2H₂O→CO₂+2H₂  (2)

C+CO₂→2CO  (3)

C+ 1/2→CO  (4)

C+O₂→CO₂  (5)

CO+H₂O →CO₂+H₂  (6)

CO+3H₂→CH₄H₂O  (7)

The most common gasification techniques comprise co-currentgasification, in which the fuel and air mainly flow into the samedirection, counter-current gasification, in which the air is suppliedfrom below and the fuel from the top of the reactor, fluidized bedreactor and entrained flow gasifier.

Integrated Gasification Combined Cycles (IGCC) developed for industrialpurposes are based on these different gasification methods (oxygen orair gasification, entrained flow, fluidized bed or fixed bed reactors)and different gas purification methods (chemical or physicalpurification, such as wet scrubbing or thermal purification).

The main components of the product or synthesis gas mixture formed as aresult of the gasification are carbon monoxide and hydrogen. In additionto these, the mixture may as impurities contain for instance CO₂ (carbondioxide), CH₄ (methane), H₂O (water), N₂ (nitrogen), H₂S (hydrogensulphide), NH₃ (ammonia), HCl (hydrogen chloride), tar and smallparticles, such as ash and carbon black. This synthesis gas may also bereferred to as woodgas, in case the fed biomass is wood.

Synthesis gas may be used as fuel as such, or the gas may be treatedfurther in order to prepare gaseous or liquid fuels or chemicals byusing different methods, such as Fischer-Tropsch fuel synthesis,methanol synthesis, or it may be used for hydrogen production bywater-gas exchange. In a combustion processes, flue gases need to beremoved by purification, whereas in gasification the removablesubstances comprise product gas particles, alkali metals, nitrogen, tar,sulphur and chlorine. Gas purification may also comprise adding hydrogento the synthesis gas in order to create a hydrogen-carbon monoxide ratiosuitable for a Fischer-Tropsch process.

Various physical purification methods may be used for purifyingsynthesis gas mixtures, for instance Selexol® (UOP LLC), Rectisol®(Lurgi AG) or Purisol® (Lurgi AG), and/or chemical purification methodssuch as amine wash.

Rectisol® is a physical gas purification process, in which methanol istypically used as the organic solvent in a below-zero temperature.Rectisol® processes are preferably performed in high pressures, whichusually exceed 30 bar.

Synthesis gas may be transformed into synthetic fuel by Fischer-Tropschsynthesis (FT-synthesis). FT-synthesis is a catalytic chemical reactionin which carbon monoxide and hydrogen are transformed into differentliquid hydrocarbons. Before the actual FT-synthesis, the synthesis gasmixture needs to be purified. The H₂/CO molar ratio of the synthesis gasfed into the FT-reactor is preferably between 2.5:1 and 0.5:1, morepreferably between 2.1:1 and 1.8:1, and most preferably about 2:1 or1:1, depending on the catalyst used.

In FT-synthesis, synthesis gases CO and H₂ react exothermically, formingmainly aliphatic hydrocarbons. In addition to paraffins, smaller amountsof olefins, primary alcohols and water are formed. The hydrocarbonsynthesis occurs according to the following reactions:

CO+2H₂→—(CH₂)—+H₂O  (8)

CO+H₂O →CO₂+H₂  (9)

2CO+H₂→—(CH₂)—+CO₂  (10)

Cobalt or iron is used as the reaction catalyst. Of these two, cobaltresults in a better conversion, and a cobalt catalyst also exhibits alonger life span. From the FT-reaction, a mixture of hydrocarboncompounds of different lengths is obtained, and this may be steered intothe desired direction by selecting a suitable reactor and a catalyst andby adjusting temperature, pressure and retention time. Typical reactionconditions range from 200° C. to 350° C. and from 15 bar to 40 bar. Inhigher temperatures, mainly short-chain compounds are synthesized,whereas in lower temperatures more long-chain hydrocarbons are formed.By-products, which have been separated from the end-product bydistillation, may be supplied to the chemical industry to be used as rawmaterials. The end products of the FT-process contain no sulphur oraromates. Fuel produced by using this technology may be mixed withlow-sulphur fossil fuels.

US 2007/0100003 A1 discloses a biomass gasification method, whereincarbon-rich material is pyrolyzed, after which the obtained bio oil andcharcoal are treated further in a rotary entrained flow gasifier.

Pulp is produced from wood mainly in two different ways, by mechanicalor chemical treatment. During chemical treatment, wood chip or non-woodmaterial is treated with heat and chemicals such as lye, separating thefibres in the wood material from each other and dissolving lignin, thebinding substance that keeps the fibres together. Alternatively, thewood may be mechanically kneaded. Friction transforms mechanical workinto heat, which softens the lignin that binds the wood fibres togetherand opens the bindings between the fibres. As a result of thistreatment, wood is made into a mass (a chemical or a mechanical mass),which is washed and most often bleached. If the mass preparation isintegrated into a paper mill, the mass may be led directly fromwash/bleaching into mass treatment in a paper machine. If this is notpossible, the mass is dried and baled for later use. The mass may alsobe supplied to a paper mill which does not have its own mass production.

In a paper mill, mass is treated in several steps before it is fed intothe headbox. Large particles such as splinters are removed from themass, it is diluted by adding water and various additional substancesare added thereto, for instance retention agents and fillers. The mainadvantages of added fillers comprise increased opacity, control of mattor bright finish, and diminished raw material costs. The fibre mass fedinto the headbox contains more than 90 percent of water.

From the headbox, the fibre mass is fed onto a moving, water-permeablewire, and as water is removed, a continuous paper web is formed on thewire. Water is first removed from the paper web by sucking water troughthe wire and then by using a wet press, after which the wire is finallytransferred into a dryer section, where final drying is performed byusing heated cylinders provided in the dryer section. The dried paperweb is cut and wound into final products.

Various coatings and surface treatment agents may be added to thefinished paper, which improve the paper characteristics, making it moresuitable for its intended use.

The filler agents used in papermaking may comprise for instance pigmentsoriginating from rock material. Up to a third of the composition of ahigher-quality paper may comprise minerals. Besides as fillers, mineralsare in top-quality papers or boards used as special coating agents. Thepurpose of the use of minerals is to prevent ink from absorbing into thepaper, whereby more precise letters are obtained. Another purpose of theminerals is to reflect light so that the print does not shine throughthe paper. By this way, a clear contrast may be created between ink andwhite paper. Minerals also slow down the breakdown of the paper, thuslengthening its life. Most commonly used minerals include kaoliniteclay, calcium carbonate and talc.

Synthetic or precipitated calcium carbonate (PPC) is commonly preparedfor the purposes of the paper industry in a so-called satellite mill inconnection with the paper mill, by using the flue gas produced in themill integrate as the carbon dioxide source and supplying theprecipitated calcium carbonate that is suitable for use in papermakingdirectly into the process.

Calcium carbonate is produced from calcium oxide (CaO), i.e. burned limeor unslaked lime, which is obtained by heating quarried limestone,CaCO₃, in a lime kiln at a temperature of about 1,000° C. Calcium oxideis mixed with water, whereby a water suspension containing slaked lime,i.e. calcium hydroxide (Ca(OH)₂), is formed (called cream of lime). Theobtained calcium hydroxide is carbonated by using pure carbon dioxide orfor instance carbon dioxide obtained from flue gases or lime kilnexhaust gases, whereby calcium carbonate and water are obtained. In casethe neutralization of the slaked lime by carbon dioxide is incomplete,excess calcium hydroxide may lead to an overly high alkalinity.

Precipitated calcium carbonate may, if desired, also be prepared byadding the calcium ions (for instance in the form of calcium hydroxide)and the carbon dioxide directly into the papermaking process (in-situ).The precipitated calcium carbonate is typically prepared by a batchprocess.

The content of the above-mentioned patent application US 2007/0100003 A1is herewith included in the present application in its entirety.

BRIEF DESCRIPTION OF THE INVENTION

The object of the invention is to utilize the carbon dioxide streamgenerated in oxygen gasification of organic matter. More specifically,the object of the invention is the use of the said carbon dioxide streamfor carbonating the calcium used in the manufacture of paper and board.In particular, the said carbon dioxide stream comprises pure andpressurized carbon dioxide produced during the manufacture of synthetichydrocarbon chains.

The invention is characterized in the features presented in theindependent claims, and preferred embodiments of the invention arepresented in the dependent claims.

Therefore, the invention relates to the use of the carbon dioxide streamgenerated in oxygen gasification of organic matter for carbonatingcalcium from a liquid containing calcium ions.

A further object of the invention is a papermaking process, in whichorganic matter is gasified with oxygen in order to carbonate calcium,the produced carbon dioxide stream is reacted with a liquid containingcalcium ions and the carbonated calcium is added to the pulp during thepapermaking process as a filler or onto finished paper as a coating.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 presents the oxygen gasification process of organic matterintegrated into the continuous manufacturing process of calciumcarbonate and papermaking.

DETAILED DESCRIPTION OF THE INVENTION

The inventors have surprisingly found that the excess carbon dioxideproduced as a by-product in biomass gasification and production ofsynthetic hydrocarbons may advantageously be used for carbonatingcalcium.

Biomass that has been treated by oxygen gasification and the carbondioxide stream generated from this biomass for example in connectionwith biofuel production may be used entirely or in part, using only thatpart which is not used in gasification or the production process, forcarbonating calcium. In the papermaking process, the carbon dioxidestream may be utilized for carbonating calcium in order to prepare asuitable amount of precipitated calcium carbonate.

Unless otherwise specified in the application, the terms used in thespecification and claims have the following meanings:

The term “organic matter” refers to biomass, in other words organicmatter that is of biological origin, such as wood or wood-based feed(for instance wood-based by-products of forestry and felling, forinstance trees removed in thinning, stubs, rootstocks, branches,brushwood and bark), agricultural waste, municipal waste, by-products offorest industry (such as tall oil soap, tall oil, black liquor andturpentine), waste water slurry of forest industry (for instance thefibre-containing matter carried to waste water in papermaking),wasteland or plants. The raw material used may also comprise wastes orby-products of various industrial processes, marine raw materials suchas algae or combinations of all the above. Preferably, the raw materialsused comprise wastes or products of wood-processing industry, such aswood residue, urban wood waste, lumber waste, wood chips, sawdust,straw, firewood, wood materials, paper, by-products of papermaking andwood production, short rotation crops such as willow, poplar, blacklocust, eucalyptus and lignocellulose cereal crops such as reed canarygrass, Miscanthus and switchgrass. The used raw materials may alsocomprise vegetable oil, animal fat, fish oil, natural wax and fattyacid.

The term “synthetic hydrocarbon chain” refers to synthetically createdshort- and long-chain hydrocarbons.

The term “oxygen gasification” refers to gasification performed in thepresence of pure oxygen (not air) and water vapour.

The present invention relates to the use of the carbon dioxide streamproduced in oxygen gasification of organic matter for carbonatingcalcium from a liquid containing calcium ions. Preferably, the saidhydrocarbon stream has been formed as a by-product of the production ofsynthetic hydrocarbon chains, for instance in connection with biofuelproduction. Preferably, at least one physical purification method thatrequires a high-pressure synthesis gas mixture and Fischer-Tropschsynthesis are used for producing synthetic hydrocarbon chains.

In a preferred embodiment, the said organic matter comprises biomasssuch as wood-based feed, agricultural waste, by-products of forestindustry, waste water slurry of forest industry, or municipal waste. Thewood-based feed comprises wood-based by-products of forestry andfelling, for instance trees removed in thinning, stubs, rootstocks,braches, brushwood and bark.

Preferably, gasification is performed in a gasifier with a fluidized bedreactor, in which the solid biomass burns at least in part. Thefluidized bed may be either a circulating or a bubbling fluidized bed,in which pure oxygen and steam are used as the fluidizing gas. Beforepure oxygen and steam are led into the fluidized bed reactor, these arepreferably, but not necessarily, combined with each other. Biomass ispreferably fed to the gasifier by using a lockhopper. In the gasifier,solid biomass reacts endothermically with steam, forming carbon monoxideand hydrogen, and exothermically with oxygen, forming carbon monoxide,carbon dioxide and additional steam. As a result of the gasification,impure synthesis gas is thus obtained, which in addition to carbonmonoxide and hydrogen contains CO₂ (carbon dioxide), CH₄ (methane), H₂O(water), N₂ (nitrogen), H₂S (hydrogen sulphide), NH₃ (ammonia), HCl(hydrogen chloride), tar and small particles, such as ash and carbonblack. The impure synthesis gas is purified and treated in severalsteps. For instance tar, methane and solid particles are removedtherefrom. Furthermore, the hydrogen/carbon monoxide ratio of thesynthesis gas is adjusted to a suitable level, after which the synthesisgas is purified by using a physical purification method such asRectisol®, and/or a chemical purification method such as amine wash, bywhich for instance purified synthesis gas as well as pure andpressurized carbon dioxide are obtained. The pure synthesis gas is ledfor instance into a Fischer-Tropsch reactor in order to producesynthetic hydrocarbon chains.

The pure and pressurized carbon dioxide stream formed as a by-product inthe production of synthetic hydrocarbon chains is especially well suitedfor carbonating calcium in a continuous reactor. The pure andpressurized carbon dioxide accelerates the carbonating reaction ofcalcium as compared to the carbon dioxide obtained from flue gases, thusenabling the use of a continuous reactor and decreasing the neededreactor size.

The regular carbon dioxide generated in a factory area andconventionally used for carbonating calcium contains a substantialamount of nitrogen. If such carbon dioxide-containing gas would be usedin a pressurized state, the presence of nitrogen would lead totroublesome bubbling and foaming, since nitrogen does not dissolve inthe carbonating solution. Pure pressurized carbon dioxide does notbubble or foam, since the carbon dioxide dissolves in the liquid,forming carbonic acid that reacts with calcium atoms.

The carbon dioxide obtained in the production of synthetic hydrocarbonchains is pure and high-pressurized to begin with, and it may even beled directly into a continuous carbonating reactor, where reaction timesare substantially shorter than in a batch reactor. In a continuousreactor, the carbonation reaction may proceed in a matter of seconds,whereas in a batch reactor the same process may last up to severalhours.

In a preferred embodiment, the purity of the carbon dioxide stream ismore than 90%, preferably more than 95%, more preferably more than 97%and most preferably more than 99% by weight. The pressure of the carbondioxide stream may be more than 5 bar, preferably more than 20 bar, mostpreferably more than 30 bar. The higher the pressure, the faster thecarbonation reaction. In case the pressure of the carbon dioxide streamis not sufficiently high, it may be raised by using a separatecompressor to a pressure of 10 bar, preferably more than 20 bar, mostpreferably more than 30 bar.

The gasification according to the invention is performed by using oxygeninstead of air, and in this process the nitrogen content of thesynthesis gas mixture is low. This comprises one more reason why thecarbon dioxide stream according to the invention is well suitedespecially for carbonating calcium in a continuous reactor, since acontinuous process is more sensitive to impurities than a batch process.In some embodiments, the carbon dioxide stream according to theinvention has a sulphur content of less than 1 ppm, and a nitrogencontent of less than 10%, preferably less than 5%, more preferably lessthan 3%, and most preferably less than 1% by weight. Preferably, thepressure of the continuous reactor is more than 5 bar, preferably morethan 10 bar, more preferably more than 20 bar, and most preferablybetween 20 bar and 30 bar. The low nitrogen and sulphur content of thecarbon dioxide stream enables the especially advantageous carbonation ofcalcium in the production of precipitated calcium carbonate.

The carbon dioxide stream according to the invention may be used forcarbonating calcium in a batch reactor of a batch process, or in asemi-continuous process, or in an in-situ papermaking process. Anespecially preferred combined efficiency is obtained, as the pure andpressurized carbon dioxide stream is led directly into the carbonatingreaction of calcium carbonate, especially into a continuous calciumcarbonate precipitation reactor.

Even though the fuels produced from biomass do not in theory add to theatmospheric carbon dioxide content since the fuels merely release thecarbon dioxide bound to the biomass from air during its lifetime, alsoemissions created during the production process need to be taken intoaccount. According to the invention, the carbon dioxide formed as aby-product is bound to calcium by a chemical reaction, and no carbondioxide is therefore released into the atmosphere, making its furthertreatment unnecessary. As far as emission rights are concerned, thebinding of carbon dioxide in the process according to the inventionenables emissions in some other process. The diminished carbon dioxideamount is, of course, also commercially exploitable.

In a preferred embodiment of the invention, the gasification and/or fuelproduction process of organic matter is integrated into a facility forcarbonating calcium, which leads to a diminished need for transports andenergy savings. The gasification of organic matter and/or the productionof fuel thereform, as well as the carbonation of calcium preferably takeplace in the same factory area, in which case the pressure of the carbondioxide may be directly utilized in the carbonation process and thecondensation and transport of carbon dioxide become unnecessary.Preferably, there is at least one papermaking process in the factoryarea.

An excellent combined effect is obtained, as the precipitated calciumcarbonate produced in the process of the invention is used in the samefactory area as a filler and/or a coating agent in the manufacture ofpaper and/or board.

The invention also relates to a process for producing paper or board, inwhich organic matter is gasified with oxygen in order to carbonate thecalcium, the generated carbon dioxide stream is reacted with a liquidcontaining calcium ions, and the carbonated calcium is added to the pulpduring the papermaking process as a filler or onto finished paper as acoating.

Preferably, the said carbon dioxide stream is formed as a by-product inthe manufacture of synthetic hydrocarbons, for instance in connectionwith the production of biofuels, and the purity of the said carbondioxide stream is preferably more than 90%, preferably more than 95%,more preferably more than 97%, and most preferably more than 99% byweight, and the pressure is more than 5 bar, preferably more than 10bar, more preferably more than 20 bar, most preferably more than 30 bar.Preferably, the carbon dioxide stream according to the invention has ahydrogen sulphide content of less than 5 ppm, preferably less than 3ppm, more preferably less than 1 ppm, and a nitrogen content of lessthan 10%, preferably less than 5%, more preferably less than 3% and mostpreferably less than 1% by weight. In a preferred embodiment, theproduction of the synthetic hydrocarbon chains is performed by usingphysical purification, such as Rectisol®, which requireshigh-pressurized synthesis gas mixture, preferably more than 10 bar,more preferably more than 20 bar and most preferably more than 30 bar,for which reason the synthesis gas mixture is therefore pressurizedbefore the purification and/or Fischer-Tropsch synthesis.

In the process that is the object of the invention, the carbonation ofcalcium may be performed in a continuous reactor by using a pressurethat is preferably more than 5 bar, preferably more than 10 bar, morepreferably more than 20 bar, most preferably between 20 bar and 30 bar,in a batch process of a batch reactor or in a semi-continuous reactor.Preferably, the carbonation is integrated directly into a papermakingprocess. The carbonation of calcium from a calcium-containing liquid mayalso be performed in-situ in the papermaking process by adding thecalcium ions and the carbon dioxide directly into the calcium-containingprocess liquid.

In the papermaking process, paper mass in diluted before the headbox ofthe paper machine by adding water, and calcium carbonate that has beencarbonated according to the invention is added to the mass or,alternatively, the carbon dioxide stream according to the invention isadded directly to the paper machine in order to carbonate the calciumions.

In a preferred embodiment, the said organic matter comprises biomass,such as wood-based feed, agricultural waste, by-products of forestindustry or municipal waste, wherein the wood-based feed may comprisewood-based by-products of forestry and felling, for instance treesremoved in thinning, stubs, rootstocks, branches, brushwood and bark.

In one embodiment, the method comprises the manufacture of precipitatedcalcium carbonate, and this manufacture is adjusted according to theneeds of the papermaking process, the feed of the said carbon dioxidestream being adjusted according to the calcium carbonate need.Preferably, the gasification of organic matter and/or the treatment ofgas is integrated into the carbonation of the calcium and papermaking inorder to efficiently utilize the formed carbon dioxide stream, thusdiminishing emissions.

Alternatively, the gasification of organic matter and/or treatment, thecarbonation of calcium and papermaking takes place in the same factoryarea in order to shorten transports.

FIG. 1 presents one preferable embodiment of the invention, in whichfeed 1 is led into gasification 2, wherein the feed is gasified by usingoxygen and steam, forming a synthesis gas mixture 3. The synthesis gasmixture 3 is objected to chemical and/or physical purification 4, bywhich three gas streams are obtained: a sulphur-containing gas stream 5,a synthesis gas stream 6 and a carbon dioxide stream 7. The synthesisgas stream 6 is transferred into Fischer-Tropsch synthesis 8, by whichbiofuel 9 is obtained. The carbon dioxide stream 7 is led directly intopaper machine 13 for the in-situ carbonation of calcium and/or to thecontinuous production of precipitated calcium carbonate in continuousreactor 10. The precipitated calcium carbonate may alternatively beprepared by a batch process. Calcium carbonate 11, 12 is led, on onehand, to a paper machine 13 to be used as a paper filler and, on theother hand, to a paper coating process 15, into which the paper moves asa paper web 14.

In a more preferred case, the wood-based by-products of the woodmaterial purchased for manufacturing paper or board are utilized in thepreparation of biofuel, and the pure and pressurized carbon dioxideobtained as a by-product is used directly in the precipitation ofcalcium carbonate, which is used directly in the making of paper orboard.

The purpose of the following examples is only to further illustrate theinvention. By using the guidance obtained from the above description, aperson skilled in the art is able to use the invention in many otherways in order to utilize the carbon dioxide stream generated in theoxygen gasification of organic matter, according to the scope ofprotection of the present invention.

Example 1 Gasification of Biomass

Wood-based by-products formed during felling, such as trees removed inthinning, stubs, rootstocks, braches, brushwood and bark are crushed anddried. The biomass is gasified by using oxygen and steam, wherein thebiomass is treated in an entrained flow gasifier at high pressure andhigh temperature, whereby a synthesis gas mixture comprising carbonmonoxide, nitrogen and carbon dioxide is obtained as the product, andthis is cooled down before purification. Thereafter the synthesis gas ispurified by using the necessary chemical and physical treatments, ofwhich the Rectisol® treatment requires that the synthesis gas mixture bepressurized to 30 bar. The purified gas is led into a Fischer-Tropschreactor in order to form FT fuels. The conditions of the Fischer-Tropschsynthesis are selected so that the desired hydrocarbon chain length isobtained. The carbon dioxide stream formed as a by-product in thepurification of the synthesis gas mixture is used for carbonatingcalcium. The nitrogen content of the carbon dioxide is less than 1% byweight, and it has a pressure of 30 bar.

Example 2 Continuous Preparation of Precipitated Calcium Carbonate

A calcium hydroxide-containing water suspension and the carbon dioxideaccording to Example 1 (99% by weight, pressure 20 bar) are led into areactor in an integrated production process of biofuel and calciumcarbonate. The pressure of the continuous reactor is 20 bar and thecalcium carbonate obtained as a product is used as a filler and acoating agent in a paper and board manufacturing process in the samefactory area. For use as a filler, the carbonated calcium is added tothe short circuit of a paper machine, where it is mixed with water andfibres in order to obtain the desired paper pulp. Calcium carbonate isalso added onto finished paper as a coating.

Example 3

Batch Production of Precipitated Calcium Carbonate

Calcium carbonate is produced from calcium oxide by a batch process.Calcium oxide is mixed with water, whereby a calciumhydroxide-containing water suspension is obtained. The thus-obtainedcalcium hydroxide is carbonated with the carbon dioxide according toExample 1 (99% by weight), which is obtained from a biofuel factorylocated in the same factory area. Calcium carbonate and water areobtained from the reaction. The precipitated calcium carbonate is useddirectly as a filler and a coating agent in a papermaking processoperated in the same factory area. Some of the precipitated calciumcarbonate is stored and used in another manufacturing process of paperand board.

1. The use of a carbon dioxide stream generated in oxygen gasificationof organic matter for carbonating calcium from a liquid containingcalcium ions.
 2. The use of a carbon dioxide stream according to claim1, characterized in that said carbon dioxide stream is formed as aby-product of the production of synthetic hydrocarbon chains.
 3. The useof a carbon dioxide stream according to claim 2, characterized in thatsaid production of synthetic hydrocarbon chains comprises production ofbiofuels.
 4. The use of a carbon dioxide stream according to claim 2,characterized in that the production of synthetic hydrocarbon chainscomprises physical purification that requires pressurized synthesis gasmixture and/or the use of a Fischer-Tropsch synthesis.
 5. The use of acarbon dioxide stream according to claim 1, characterized in that saidorganic matter comprises biomass, for instance wood-based feed,agricultural waste, by-products of forest industry, waste water slurryof forest industry or municipal waste.
 6. The use of a carbon dioxidestream according to claim 5, characterized in that said wood-based feedcomprises wood-based by-products of forestry and felling, for instancetrees removed in thinning, stubs, rootstocks, braches, brushwood andbark.
 7. The use of a carbon dioxide stream according to claim 1,characterized in that the purity of the carbon dioxide stream is morethan 99% by weight.
 8. The use of a carbon dioxide stream according toclaim 1, characterized in that the pressure of the carbon dioxide streamis more than 5 bar, preferably more than 10 bar, more preferably morethan 20 bar, most preferably more than 30 bar.
 9. The use of a carbondioxide stream according to claim 1, characterized in that the sulphurcontent of the carbon dioxide stream is less than 1 ppm.
 10. The use ofa carbon dioxide stream according to claim 1, characterized in that saidcarbon dioxide stream contains less than 10%, preferably less than 5%,more preferably less than 3%, most preferably less than 1% by weight ofnitrogen.
 11. The use of a carbon dioxide stream according to claim 1,characterized in that the calcium is carbonated in a continuous reactor.12. The use of a carbon dioxide stream according to claim 11,characterized in that the pressure of the continuous reactor is morethan 5 bar, preferably more than 10 bar, more preferably more than 20bar, most preferably between 20 and 30 bar.
 13. The use of a carbondioxide stream according to claim 1, characterized in that the calciumis carbonated in a batch reactor or in a semi-continuous reactor. 14.The use of a carbon dioxide stream according to claim 1, characterizedin that the calcium is carbonated in-situ in a papermaking process. 15.The use of a carbon dioxide stream according to claim 1, characterizedin that the gasification of organic matter is integrated into thecarbonation of calcium in order to enable the utilization of thegenerated carbon dioxide stream.
 16. The use of a carbon dioxide streamaccording to claim 1, characterized in that the gasification of organicmatter and the carbonation of calcium take place in the same factoryarea in order to enable the utilization of pressure of the carbondioxide.
 17. A process for preparing paper or board, characterized inthat organic matter is gasified with oxygen in order to carbonate thecalcium, the generated carbon dioxide stream is reacted with a liquidcontaining calcium ions, and the carbonated calcium is added to the pulpas a filler and/or onto finished paper as a coating during themanufacture of paper or board.
 18. A process according to claim 17,characterized in that said carbon dioxide stream is generated as aby-product in the production of synthetic hydrocarbon chains.
 19. Aprocess according to claim 18, characterized in that said production ofsynthetic hydrocarbon chains comprises the production of biofuels.
 20. Aprocess according to claim 18, characterized in that the synthesis gasmixture obtained by said oxygen gasification is purified by physicalpurification that requires pressurization of the synthesis gas mixtureand/or that said synthetic hydrocarbon chains are formed byFischer-Tropsch synthesis.
 21. A process according to claim 17,characterized in that said organic matter is biomass such as wood-basedfeed, agricultural waste, by-products of forest industry, waste waterslurry of forest industry or municipal waste.
 22. A process according toclaim 21, characterized in that said wood-based feed compriseswood-based by-products of forestry and felling, such as trees removed inthinning, stubs, rootstocks, braches, brushwood and bark.
 23. A processaccording to claim 17, characterized in that the purity of said carbondioxide stream is more than 90%, preferably more than 95%, morepreferably more than 97%, and most preferably more than 99% by weight.24. A process according to claim 17, characterized in that the pressureof said carbon dioxide stream is more than 5 bar, preferably more than10 bar, more preferably more than 20 bar, most preferably more than 30bar.
 25. A process according to claim 17, characterized in that saidcarbon dioxide stream contains less than 1 ppm of sulphur.
 26. A processaccording to claim 17, characterized in that said carbon dioxide streamcontains less than 10%, preferably less than 5%, more preferably lessthan 3%, and most preferably less than 1% by weight of nitrogen.
 27. Aprocess according to claim 17, characterized in that the carbonation ofcalcium is adjusted according to the needs of the papermaking processand the use of said carbon dioxide stream is adjusted according to thecalcium carbonate need.
 28. A process according to claim 17,characterized in that calcium is carbonated in a continuous reactor. 29.A process according to claim 28, characterized in that the pressure ofsaid continuous reactor is more than 5 bar, preferably more than 10 bar,more preferably more than 20 bar, most preferably between 20 and 30 bar.30. A process according to claim 28, characterized in that saidcontinuous reactor is integrated into a papermaking process.
 31. Aprocess according to claim 17, characterized in that calcium iscarbonated in a batch reactor or in a semi-continuous reactor.
 32. Aprocess according to claim 17, characterized in that calcium iscarbonated in-situ in a papermaking process.
 33. A process according toclaim 17, characterized in that the gasification of organic matter isintegrated into the carbonation of calcium and the manufacture of paperor board in order to enable the utilization of the generated carbondioxide stream.
 34. A process according to claim 17, characterized inthat the gasification of organic matter, the carbonation of calcium andthe manufacture of paper or board take place in the same factory area.